Generally a wearable device has a small volume, for which a large touch screen similar to that of a tablet computer or many keys similar to that of a keyboard cannot be provided. Therefore, a user controls the wearable device or controls other electronic devices via the wearable device by moving at least one part of a body of the user. For example, the user rotates a wrist on which a smart watch is worn.
The user can determine whether a motion of the user is obtained by the wearable electronic device by observing whether the wearable device or other electronic devices make a response in a case that the motion of the at least one part is finished. The user cannot determine whether the motion of the at least one part of the body of the user is valid for the electronic device during a motion process. In other words, the conventional wearable device cannot prompt the user regarding whether the motion of the at least one part is obtained by the electronic device.